John Deere 520543.04 – TEC, RLC, AIC, or OIC: CAN BUS Voltage Low

Voltage on the CAN Low (CAN-) communication wire has dropped below the acceptable operating threshold. This condition is almost always caused by a short to ground on the CAN- circuit, a failed terminating resistor, or an internal short within a module's CAN transceiver.

• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 8225R
• 8245R
• 8270R
• 8295R
• 8320R
• 8335R
• 8345R
• 8370R
• 8400R
• 210L EP Tractor Loader
• 310K Backhoe Loader

1. 1

   Cycle the ignition OFF and ON to clear temporary software glitches and ensure the module firmware is updated to the latest version

2. 2

   Perform a termination resistance test: disconnect batteries and measure resistance across CAN High and CAN Low pins at a diagnostic port (should read approximately 60 ohms)

3. 3

   Perform a short to ground test: with batteries disconnected, measure resistance between the CAN Low (CAN-) pin and a clean chassis ground (low resistance confirms a short)

4. 4

   Isolate the short: disconnect the harness connector at the Cab Roof Module and re-check the CAN Low wire for a short to ground (if short disappears, the module is faulty; if it remains, the harness is damaged)

5. 5

   Inspect the A-pillar connectors and roof module connectors for backed-out pins, corrosion, or loose crimps

1. 1

   Disconnect battery

   Turn off the ignition and disconnect the negative battery cable to prevent transient current spikes that can blow polyfuses or damage other transceivers.

2. 2

   Access module

   Remove the interior cab roof panel to access the TEC or RLC Cab Roof Module.

3. 3

   Disconnect harness

   Disconnect the main wiring harness from the module.

4. 4

   Repair harness or replace module

   Based on your diagnostic isolation test: If the harness is shorted, trace the CAN- wire down the cab's A-pillar and along the chassis routing. Look for pinch points where the wire insulation has rubbed through against the metal frame. Cut out the damaged wire section, solder in a replacement wire, and seal it with heat-shrink tubing. If the module is shorted, unbolt the faulty TEC or RLC module from its mounting bracket. Install the replacement module and secure the mounting hardware.

5. 5

   Reconnect harness

   Reconnect the wiring harness to the module, ensuring the connector locks firmly into place.

6. 6

   Reconnect battery

   Reconnect the negative battery cable.

7. 7

   Clear fault code

   Turn the ignition ON. Connect a diagnostic tool (such as John Deere Service ADVISOR or Jaltest) to clear the stored 520543.04 fault code.

8. 8

   Verify repair

   Start the machine and run it at working RPM to verify the code does not return under vibration.